Air filters are commonly used to filter the air supply to a standard internal combustion engine, e.g., automotive engines, truck or heavy equipment engines, and stationary power sources. The intake air must be filtered to remove dust, dirt, and other contaminants which may damage or reduce the efficiency of the engine. In all of these applications, the filter must be changed periodically.
Conventional air filters have a permanent housing which is openable for access to a filter element which is located inside the housing. To perform a filter change, the housing is opened, the filter element removed, a new filter inserted into the housing, and the housing closed. The housing is connected to the engine through an intake air tube. Unfortunately, conventional air filters present a number of significant disadvantages.
The use of conventional air filters creates an increased risk of unfiltered air reaching the engine. As noted above, conventional air filters have a removable filter element located inside the filter housing. Accordingly, it will be appreciated that the filter element must sealingly engage the interior of the housing to prevent unfiltered air from bypassing the filter element. It is difficult, however, to ensure that an airtight seal has been formed. The filter element must be inserted in the housing so that it is properly oriented with the sealing structure of the housing interior. Furthermore, the filter element is not permanently placed inside the housing but instead is routinely replaced, thereby requiring accurate installation on a regular basis. The use of a number of different elements with a single filter housing creates the potential for inconsistencies in the different filter elements which may affect the quality of the seal formed with the housing. Finally, dirt or other foreign material may contaminate the sealing surface, thereby reducing the chances of forming a complete seal.
Conventional air filters are also overly burdensome to replace. When removing and replacing a filter element from a filter housing, care must be taken to prevent dirt or other debris from entering the air intake tube and, ultimately, the engine. It will be appreciated that during operation, dirt particles collect in the filter element and on the interior surface of the housing. During filter element replacement, the filter element is often tipped or bumped in a manner which knocks loose dirt particles from the element and into the housing, thereby adding to the amount of particles already collected on the interior surface of the housing. The housing therefore must be thoroughly cleaned during filter changes to prevent dirt from reaching the air intake tube. Extra care must be taken to ensure that the dirt is actually removed, rather than relocated, during cleaning, since any remaining dirt will be drawn into the engine during subsequent operation. Particular attention must be given to the sealing surface of the housing so that an optimum sealing surface is obtained. The cleaning of the housing and the care which must be taken during filter element removal make conventional air filters overly costly, burdensome, and time consuming to replace.
Conventional air filters further create additional costs for OEM applications. Engine manufacturers must fabricate and assemble the filter housings. The manufacturer must not only provide the raw materials to form the housing, but must also have appropriate tooling on hand to fabricate the housings. Tooling costs are significant, considering the relatively low volume of housings (i.e., one per engine) needed compared to the multiple filter elements required during the life of the engine. Because of the low volume, the per unit costs to OEM manufacturers to fabricate filter housings is overly high.
Alseth et al., U.S. Pat. No. 4,350,509, discloses a disposable air cleaner in which the filter element is permanently attached to the filter housing, thereby addressing some of the shortcomings noted above. Alseth, however, discloses end caps made entirely of a lightweight material, such as urethane, which is directly exposed to the operating environment of the air filter. As a result, it has been found that the housing of the Alseth device is susceptible to mechanical and thermal damage. For example, at the high temperature end, it has been found that the device of Alseth tends to deform at around 210-230.degree. F.
In addition, to properly support the device of Alseth, the engine manufacturer must provide a rigid air intake tube which extends entirely through an inner aperture of the filter. It will be appreciated that the end of the air intake tube inserted into the Alseth device must further be perforated to allow air flow through the filter. Alseth therefore requires specially formed parts for mounting and therefore is overly costly to engine manufacturers. Furthermore, the device of Alseth requires additional engine space so that the filter may be slid over the air intake tube.